Since the barrels are "Cut Off" ahead of the chamber it should be perfectly obvious that it is first necessary to remove the ribs. These are most often soft soldered on. The breeches are mast often brazed, including the underlug as well as the rear portion of the top rib if it has an upper bolt. These would be left intact. The sleeve joint itself does not weaken the chamber area. "IF" the old barrels had rust or pitting inside the ribs then it is highly conceivable the sleeved barrels are indeed stronger & they may well be made of a stronger alloy of steel than were the old ones.
I would of course never recommend sleeving a set unless the old barrels had been determined to be UN-SAFE. n that case it has been & still can be a very viable means of putting a fine old gun back into use. One simply has to weigh the cost against what can be obtained for the same money otherwise. Assuming a well-done job, safety is not truly the issue.
